1). Field of the Invention
This invention relates to a system and method for manufacturing a part.
2). Discussion of Related Art
It has become common place to fabricate three-dimensional components using Computer Numerical Control (CNC) systems. State of the art solid freeform fabrication (SFF) methods span a number of technologies including stereolithography, 3D printing, selective laser sintering, direct metal deposition, electron beam melting, and microplasma powder deposition. Thermoplastic-based SFF technologies allow designers to verify product design with three-dimensional models at an early stage, but are not capable of fabricating high-strength end products. In principle, metal-based SFF technologies allow for the rapid manufacture of structurally sound, dimensionally accurate metallic parts directly from computer aided design (CAD) models. Laser-based SFF technologies (e.g. DMD and SLS) are highly dependent on specific process parameters to achieve structurally sound parts. These process parameters are specific to the composition, morphology, and materials properties of the metallic powder, as well as the characteristics of the laser beam used to consolidate the powder. Selective Laser Sintering (SLS) and Direct Metal Deposition (DMD) are examples of three-dimensional additive manufacturing systems wherein a high power laser is used to fuse components or particles, such as metal powders or ceramic/metal composite powders, to one another as a means of building up a macroscopic part. These components or particles to be fused may be located in a dense particle bed, as in SLS, or may be entrained in a gas flow and fused in a weld pool on the surface of the part being manufactured, as in DMD. However, in both SLS and DMD technologies, the entire unfused components or particles that comprise the powdered material is heated indiscriminately by the high intensity laser beam. In certain applications, such as when the powdered material includes a ceramic component, the laser may cause thermal decomposition of the ceramic part resulting in the degradation of the physical characteristics of the macroscopic part.
Additive Manufacturing (AM) is a manufacturing process in which complex parts are fabricated by the fusing together of small individual components to create a large macroscopic part. Typically, the small individual components are particles in a powder of a specific material. In powder bed AM systems, for example, complex parts are usually fabricated through the layer-by-layer consolidation of the particles in a powder bed. This consolidation can be realized through the input of energy to the particles, which causes the particles to heat, sinter, and/or melt together or otherwise connect to one another to form a dense solid. Energy can be delivered to the particles by using a laser, electron beam, or by exposing the material to a high frequency magnetic field.
In conventional powder bed AM, each layer of powder is consolidated sequentially to form the complex part. An earlier layer holds a subsequent layer that is deposited. During the fabrication process, particles of the topmost layer of loose powder are fused to both the parent part (i.e. the substrate or an earlier layer) and the neighboring loose particles. This is accomplished by using spatially compact energy sources (e.g. laser, electron beam, high frequency magnetic fields, etc.) to locally consolidate the particles in a specific pattern defined by a two-dimensional cross section of the three-dimensional (3D) part.